1. Dalhousie University Department of Physics and Atmospheric Science Materials Science Biophysics Condensed Matter Physics Atmospheric Science Research in Theoretical, Experimental, and Applied Physics

2. A Satellite’s View of Tropospheric Chemistry Daniel Jacob Paul Palmer Dorian Abbot Mathew Evans Randall Martin Kelly Chance Thomas Kurosu

3. CHALLENGE FOR THE NEXT DECADE: IMPROVE EMISSION INVENTORIES “Half of all Canadians live in regions failing to achieve compliance with the surface ozone standard” “Nova Scotians with lung problems should stay inside until pollution levels drop warned Environment Canada”

4. TROPOSPHERIC OZONE IS A KEY SPECIES IN CLIMATE AND AIR QUALITY Tropopause Stratopause Major greenhouse gas Primary constituent of smog Largely controls atmospheric oxidation Stratosphere Troposphere Ozone layer Mesosphere

5. Historical records imply a large anthropogenic contribution to the present-day tropospheric ozone background at northern midlatitudes Ozone trend from European mountain observations, 1870-1990 [Marenco et al.,1994]

6. ? ? ? FiresBiosphereHuman activity Nitrogen oxides (NO x ) CO, Volatile Organic Compounds (VOCs) Ozone (O 3 ) Hydroxyl (OH) GLOBAL BUDGET OF TROPOSPHERIC OZONE hvhv,H 2 O Global sources and sinks, Tg O 3 yr -1 (GEOS-CHEM model) Chem prod in troposphere 4900 Chem loss in troposphere 4200 Transport from stratosphere 500 Deposition 1200 Formaldehyde (HCHO)

7. BOTTOM-UP EMISSION INVENTORIES ARE NOTORIOUSLY DIFFICULT TO DETERMINE Fuel use estimates Measurements of emission ratios Process studies Estimate biological density Temperature, water, … dependence of biological activity Extreme events "Trees cause more pollution than automobiles do."

8. HOW DO WE EVALUATE AND IMPROVE A PRIORI BOTTOM-UP INVENTORIES? Surface NO X Isoprene during July GEIA Global NOx Emissions (Tg N yr -1 ) Fossil Fuel 24 (20-33) Biomass Burning 6 (3-13) Soils 5 (4-21) North American Isoprene Emissions (3-15 Tg C yr -1 )

9. TOP-DOWN INFORMATION FROM THE GOME SATELLITE INSTRUMENT Operational since 1995 Nadir-viewing solar backscatter instrument (237-794 nm) Low-elevation polar sun- synchronous orbit, 10:30 a.m. observation time Spatial resolution 320x40 km 2, three cross-track scenes Complete global coverage in 3 days

10. SPECTROSCOPY CAN BE APPLIED TO OTHER STARS AND THE EARTH’S ATMOSPHERE Figure adapted from Ian Short Weaker lines of nitrogen dioxide (NO 2 ) and formaldehyde (HCHO)

11. PERFORM A SPECTRAL FIT OF SOLAR BACKSCATTER OBSERVATIONS absorption wavelength   Slant optical depth EARTH SURFACE Scattering by Earth surface and by atmosphere Backscattered intensity I B “Slant column” Solar I o

12. USE GOME MEASUREMENTS TO RETRIEVE NO 2 AND HCHO COLUMNS TO MAP NO x AND VOC EMISSIONS Emission NO NO 2 HNO 3 lifetime <1 day NITROGEN OXIDES (NO x )VOLATILE ORGANIC COMPOUND (VOC) Emission VOC OH HCHO hours CO hours BOUNDARY LAYER GOME NO / NO2   W ALTITUDE Tropospheric NO 2 column ~ E NOx Tropospheric HCHO column ~ E VOC

13. K. Chance GOME HCHO SLANT COLUMNS (JULY 1996) Hot spots reflect high VOC emissions from fires and biosphere BIOGENIC ISOPRENE IS THE MAIN SOURCE OF HCHO OVER U.S. IN SUMMER

14. SLANT COLUMNS OF NO 2 FROM GOME Dominant stratospheric structure (where NO 2 is produced from N 2 O oxidation) Also see tropospheric hot spots (fossil fuel and biomass burning) Remove strat & instrument artifacts using obs over Pacific Martin et al., 2002

15. SLANT COLUMNS OF TROPOSPHERIC NO 2 FROM GOME 1996 Martin et al., 2002

16. GEOS-CHEM MODEL Assimilated Meteorology (GEOS) 2 o x2.5 o horizontal resolution, 26 layers in vertical O 3 -NO x -hydrocarbon chemistry Radiative and chemical effects of aerosols Emissions: –Fossil fuel: GEIA (NOx), Logan (CO), Piccot (NMHCs) –Biosphere: modified GEIA (hydrocarbons) & Yienger/Levy (soil NO x ) –Lightning: Price/Rind/Pickering, GEOS convective cloud tops –Interannually varying biomass burning Cross-tropopause transport Deposition

17. IN SCATTERING ATMOSPHERE, AMF CALCULATION NEEDS EXTERNAL INFO ON SHAPE OF VERTICAL PROFILE d()d() IoIo IBIB EARTH SURFACE RADIATIVE TRANSFER MODEL Scattering weight ATMOSPHERIC CHEMISTRY MODEL “a priori” Shape factor Calculate w(  ) as function of: solar and viewing zenith angle surface albedo, pressure cloud optical depth, pressure, frac aerosol profile, type INDIVIDUAL GOME SCENES NO 2 mixing ratio C NO2 (  ) norm. by column Ω NO2  (  ) is temperature dependent cross-section sigma (  )

18. Clear-sky NO 2 AMF Fraction of I B From Clouds Actual NO 2 AMF accounting for clouds JULY 1996 Martin et al., 2002

19. VERTICAL COLUMNS CONFINED TO REGIONS OF SURFACE EMISSIONS Cloud/albedo artifacts removed by AMF calculation NO / NO2   WITH ALTITUDE NO x lifetime <1day Slant Vertical Martin et al., 2002

20. GOME Tropospheric NO 2 GEOS-CHEM Tropospheric NO 2 10 15 molecules cm -2 r=0.75 bias 5% Martin et al., 2003

21. STRATEGY: OPTIMIZE INVENTORIES USING A PRIORI BOTTOM-UP AND GOME TOP-DOWN INFORMATION A posteriori emissions Top-down emissionsA priori emissions A priori errors Top-down errors GOMEGEOS-CHEM

22. TOP-DOWN ERROR IN NO X EMISSIONS Spectral fit and removal of stratospheric column AMF (surface reflectivity, clouds, aerosols, NO 2 profile) GOME Spectrum (423-451 nm) Tropospheric NO 2 Slant Column 1x10 15 molecules cm -2 40% of tropospheric column Tropospheric NO 2 Column NO x Emissions NO x Lifetime (GEOS-CHEM) 30% of tropospheric column Martin et al., 2003

23. TOP-DOWN INFORMATION FROM GOME REDUCES ERROR IN NO X EMISSION INVENTORY Bottom-up error  a Mean = 2.0 Top-down error  t Mean = 2.0 Martin et al., 2003

24. OPTIMIZED NO X EMISSIONS 36.4 Tg N yr -1 37.7 Tg N yr -1 Martin et al., 2003

25. DIFFERENCE BETWEEN A POSTERIORI AND A PRIORI Annual mean ratio (A posteriori / A priori) Martin et al., 2003

26. TOMS/MLS TROPOSPHERIC OZONE SUPPORTS A PRIORI BIOMASS BURNING NO X EMISSIONS HIGH OVER INDIA Dobson Units for March, April, May TOMS/MLS GEOS-CHEM 30 N 30 S 30 N 30 S Chandra et al., 2003

27. QUANTIFY INTERANNUAL VARIATION IN NO x EMISSIONS 1997199819992000 DJF MAM JJA SON

28. ISOPRENE EMISSIONS FOR JULY 1996 DETERMINED FROM GOME FORMALDEHYDE COLUMNS GEIA (IGAC inventory) GOME COMPARE TO… Palmer et al., 2003

29. CONSISTENT WITH IN-SITU HCHO OBSERVATIONS GEIA (A priori) r 2 = 0.53 GOME (A posteriori) r 2 = 0.77 EVALUATE GOME ISOPRENE INVENTORY BY COMPARISON WITH IN SITU OBSERVATIONS USING GEOS-CHEM MODEL AS INTERMEDIARY

30. GOME HCHO COLUMNS SHOW SEASONAL VOC EMISSIONS Agreement in general pattern, regional discrepancies point to need for improving GEOS-CHEM isoprene emissions (in progress using GBEIS) -0.5 0 10 16 molec cm -2 2.0 2.5 GOME GEOS-CHEM (GEIA) GOME GEOS-CHEM (GEIA) APR MAR MAY JUN JUL AUG SEP OCT Abbot et al., 2003

31. HCHO INTERANNUAL VARIATION HIGHLY TEMPERATURE SENSITIVE Abbot et al., 2003 1995 1996 1997 1998 1999 2000 2001

32. Platform multipleERS-2TerraENVISATSpace station AuraTBD Sensor TOMSAVHRR/ SeaWIFS GOMEMOPITTMODIS/ MISR SCIAMA CHY MIPASSAGE-3TESOMIMLSCALIPSOOCO Launch 197919951999 2002 2004 2005 O3O3 NN/LLL NL CONN/LL CO 2 N/LN NOL NO 2 NN/LN HNO 3 LL CH 4 N/LN HCHONN/LN SO 2 NN/LN BrONN/LN HCNL aerosolNNNNLNN PRESENT AND FUTURE SATELLITE OBSERVATIONS OF TROPOSPHERIC CHEMISTRY Increasing spatial resolution